CORBA::Any

Previous Topic | Next Topic | Contents | Index
Getting Started Guide | Administration Guide | Programmer's Guide

Subtopics

Description of Any

The C++ Any class implements the basic IDL Any type. The Any type permits the specification of values that can express any OMG IDL type. An Any consists of a TypeCode and a pointer to the data value. This type is for specifying values in a type-safe way, or for handling values whose type is not known when created by the C++ compiler. A process receiving a value of the Any type must determine its type before it can specify its value.

The Any type is often used with interfaces from the Interface Repository or the Dynamic Invocation Interface.

To reduce the chance of creating an Any with a mismatched typecode and value, C++ function overloading is used. The functions use overloaded operators to avoid name space problems. The Any interface requires C++ types that are generated to be distinct except for the following:

• The boolean, octet, and char IDL types are not required to map to distinct C++ types.
• Because all strings map to char*, they are distinguished using helper types in the Any class interface.
• Function overloading cannot be used to distinguish arrays of different sizes. For arrays, the _out and _forAny classes must be used directly.

CORBA::Any::Any( ) Default Constructor

Syntax

Any( );

Description

The default constructor creates an Any with a TypeCode of type CORBA::tk_null and a zero value. The easiest and safest way to construct an Any is using the default constructor as follows:

//C++
CORBA::Short s = 10;
CORBA::Any a;
a <<= s;

See Also

CORBA::Any::operator<<=( ), the other Any constructors:
CORBA::Any::Any( ) Copy Constructor
CORBA::Any::Any( ) Complex Constructor

CORBA::Any::Any( ) Copy Constructor

Syntax

Any(const Any& a);

Description

This is the Any copy constructor that duplicates the TypeCode_ptr of a and deep copies the value.

See Also

Other Any constructors:
CORBA::Any::Any( ) Default Constructor
CORBA::Any::Any( ) Complex Constructor

CORBA::Any::Any( ) Complex Constructor

Syntax

Any (typeCode_ptr <type>, void* <val>, Boolean release = 0);

Description

This constructor creates an Any with a TypeCode and value. It is needed when you cannot use the default constructor with the operator <<=( ). You might use this constructor, for example, to create an Any with a specific TypeCode for a bounded string.

This constructor is not type-safe. You must ensure consistency between the TypeCode and the type of the argument <val>.

Parameters

<type>

Refers to a CORBA::TypeCode. The constructor duplicates this object reference.

<val>

The value pointer. This value is passed to the constructor with release = 1.

release

A boolean variable to decide ownership of the storage pointed to by <val>. If it is set to 1, the Any object assumes ownership of the storage. A compliant program should not use <val> after the constructor call. If the release parameter is set to 0 (the default), the calling program is responsible for managing the memory pointed to by <val>.

See Also

Other Any constructors:
CORBA::Any::Any( ) Default Constructor
CORBA::Any::Any( ) Copy Constructor

CORBA::Any::~Any( ) Destructor

Syntax

~Any( );

Description

This is the destructor for an Any. The destructor frees the value contained in the Any based on the TypeCode of the Any. The TypeCode is also released.

See Also

CORBA::Any::Any( ) Complex Constructor

CORBA::Any::operator=( )

Syntax

Any& operator=(const Any& a);

Description

This is the assignment operator. It releases TypeCode and frees the value as necessary. It duplicates the TypeCode of a and performs a deep copy of the value of the parameter.

CORBA::Any::operator<<=( )

Syntax

void operator<<=(Short);
void operator<<=(Long);
void operator<<=(UShort);
void operator<<=(ULong);
void operator<<=(Float);
void operator<<=(Double);
void operator<<=(const char*); //Unbounded string
void operator<<=(Any&);
void operator<<=(Object_ptr);
void operator<<=(from_boolean);
void operator<<=(from_octet);
void operator<<=(from_char);
void operator<<=(from_string);

Description

This inserts a value of the specified type into an Any. Previous values held by the Any are deallocated. Each operator<<=( ) copies the inserted value. _duplicate( ) is used in the case of an object reference. The Any is then responsible for memory management of the copy.

The insertion function operator<<=(const char* <s>) considers the value passed in <s> to be an unbounded string. The function CORBA::Any::replace( ) must be used to insert a bounded string into an existing Any or from_string struct.

For function overloading, the C++ mapping for IDL types boolean, octet, and char cannot be distinguished. You must use the CORBA::Any::from_boolean, CORBA::Any::from_octet, and CORBA::Any::from_char helper classes to distinguish these types.

For example:

//C++
CORBA::Octet o = 050;
CORBA::Any a;
	
a <<= CORBA::Any::from_octet(o);

The following is invalid:

a<<= o;

Any attempt to insert an unsigned char value into an Any causes a compiler error.

See Also

CORBA::Any::replace( )

CORBA::Any::operator>>=( )

Syntax

const Boolean operator>>=(Short&) const;
const Boolean operator>>=(Long&) const;
const Boolean operator>>=(UShort&) const;
const Boolean operator>>=(ULong&) const;
const Boolean operator>>=(Float&) const;
const Boolean operator>>=(Double&) const;
const Boolean operator>>=(char*&) const;
const Boolean operator>>=(Any&) const;
const Boolean operator>>=(Object_ptr&) const;
const Boolean operator>>=(to_boolean) const;
const Boolean operator>>=(to_octet) const;
const Boolean operator>>=(to_char) const;
const Boolean operator>>=(to_string) const;
const Boolean operator>>=(to_object) const;

Description

This extracts a value of the specified type from an Any. You can determine the type of an Any by calling the member function CORBA::Any::type( ) and then extracting the value using operator>>=( ).

For function overloading, the C++ mapping for IDL types boolean, octet, and char cannot be distinguished. You must use the CORBA::Any::to_boolean, CORBA::Any::to_octet, and CORBA::Any::to_char helper classes to distinguish these types.

For example:

//C++
CORBA::Octet o;
CORBA::Any a = ...;
	
if (a >>= CORBA::Any::to_octet(o))...

The following is invalid:

if (a>>= o) ... 

Any attempt to extract an unsigned char value from an Any causes a compiler error.

The operators return 1 if the Any contains a value of the appropriate type. Otherwise, they return 0, set their parameter to 0, and return a 0 value if the Any contains no value.

The to_object helper type is used to extract an object reference for an Any as the base object type. If the Any contains a value of an object reference type as indicated by its TypeCode, the extraction function operator>>=(to_object) widens the contained object reference to Object and returns true; otherwise, it returns false. This is the only object reference extraction function that can widen the extracted object reference. The to_object operator performs no duplication of the object reference.

CORBA::Any::replace( )

Syntax

void replace(TypeCode_ptr <type>, void* <val>, Boolean release = 0);

Description

This member function is required when you cannot use operator<<=( ) to insert a value into an Any. For example, you can use this function to create an Any with a specific TypeCode for a bounded string. Note that you must ensure consistency between the TypeCode and the type of the <val> argument.

Parameters

<type>

Refers to a CORBA::TypeCode. The function duplicates this object reference.

<val>

Represents the value pointer.

release

Defines a boolean variable that determines ownership of the memory that <val> points to: 1 means the Any object gets ownership. A compliant program should not use <val> after the call. 0 means the calling program is responsible for managing the memory pointed to by <val>. The value pointed to by <val> is deep copied in the any.

See Also

CORBA::Any::operator<<=( )

CORBA::Any::type( )

Syntax

TypeCode_ptr type( ) const;

Description

This returns a reference to the TypeCode associated with the Any.

The called should not release the reference nor assign it to a CORBA::TypeCode var variable.

See Also

CORBA::Any::operator<<=( )
CORBA::Any::operator>>=( )

CORBA::Any::value( )

Syntax

void* value( ) const;

Description

This returns a pointer to the value stored in the Any. The returned value depends on the type of the value as listed in Table 1:

The calling program should not free the memory returned by the value( ) call.

See Also

CORBA::Any::type( )

Previous Topic | Next Topic | Contents | Top
Getting Started Guide | Administration Guide | Programmer's Guide
Bibliography | Glossary | Index

© Tandem, a division of Compaq. All rights reserved. Legal notices.